The record-linkage system available for residents of Rochester, Minnesota has been used to identify all possible cases of complex partial, absence, and tonic-clonic seizures diagnosed between the years 1935 and 1979 who were born in the community. Case-control studies were conducted to identify risk factors associated with these seizure types. Potential risk factors studied included mother's characteristics, complications of pregnancy, medical and surgical events during pregnancy, factors of delivery, medical or surgical events at delivery, characteristics of the newborn, and adverse medical events occurring after birth. The relationship between febrile seizures and subsequent risk of epilepsy was specifically addressed. A study of the relationship of duration of untreated epilepsy to the ease or difficulty of its subsequent treatment is being carried out in several countries. The objective of the study is to determine how critical early diagnosis and early treatment are to the patient in terms of subsequent control of epilepsy.